At present, ballast apparatus for series-sequenced gaseous discharge devices, such as T-12 fluorescent lamps, for example, usually includes a transformer coupled to a potential source and to the ends of the series-sequenced gaseous discharge devices. A filament from each one of the series-sequenced lamps is connected in parallel, and these parallel connected filaments are coupled to the transformer. Frequently, a starting capacitor is shunted across one of the pair of series-sequenced gaseous discharge devices in order to provide an increased open circuit starting potential for initiating conduction in one of the discharge devices and, subsequently, effecting energization of the other discharge device.
Although the above-described apparatus has been and still is utilized in numerous present day applications, T-12 ballast-lamp systems for example, it has been found that there are other applications wherein such apparatus leaves something to be desired. More specifically, other applications have been found wherein an increased open circuit starting voltage capability is a necessity. This added voltage capability must be designed into the ballast circuit in such a manner as to satisfy existing Underwriters Laboratories (UL) voltage limitations on socket-to-ground voltage.
One attempt to alleviate undesired excess socket-to-ground voltages is suggested in U.S. Pat. No. 4,185,231, issued Jan. 22, 1980 in the name of Colliton. Therein, a starting capacitor shunts one of a pair of series-sequenced gaseous discharge devices and a resistor is shunted across the starting capacitor and allegedly decreases undesired peak voltages appearing between the socket of a discharge device and circuit ground. However, it is obvious that the addition of a power consuming device, such as a resistor, is costly and even more significantly causes an undesired and expensive loss of power.